This invention relates to a grinding machine, and more particularly, to a grinding machine in which a sander (grinding wheel) can be controlled so as to be restricted in its oscillatory movement.
In general, a well known grinding machine has a sander against which a work abuts while the sander is rotated and moved reciprocatingly in its axial direction during a grinding or polishing.
However, there is a case that an operation is desirably performed while the sander is not moved in its axial direction. U.S. Pat. No. 1,849,868 discloses an oscillator for restricting the reciprocal movement of the sander in the axial direction. The oscillator has a cam groove at the circumferential surface of a driving shaft, and a ring member having a cam which is engaged with the cam groove is provided slidably on the outer periphery of the driving shaft. A cover for the ring member restricts the sliding movement of the ring member on the driving shaft. When the driving shaft is moved reciprocatingly in the axial direction, the ring member is covered with the cover so as to be restrained from sliding on the driving shaft. With this state, when the driving shaft is rotated, the driving shaft is reciprocatingly moved along the cam groove. In contrast, when the driving shaft is restrained from moving reciprocatingly, the cover is eliminated. With this state, the ring member is slit in the axial direction because of the engagement of the cam with the cam groove in a state wherein the driving shaft is not moved in the axial direction.
However, in the above conventional structure, even in case that the driving shaft is restrained from moving in the axial direction, the cam is engaged with the cam groove thereby to generate sound of friction. Further, a switching operation between an operation for restricting the movement of the driving shaft in its axial direction and an operation for moving the driving shaft in its axial direction is troublesome because the cover must be put on or taken off.